NAVICULA. 199 



Prof. Cleve distinguishes the following forms in N.fusca from the North 



Sea : 



var. norvegica CI. (A fusca Ad. Schm. Ad., pi. 7, f. 2-3*), plate 

 26, fig. 741. 



Valve broadly elliptic ; ro costal and ic longitudinal puncta in 1 c.d.m. 



var. subrectangularis CI. (A jusca Ad. Schm. Atl., pi. 7, f. 4*), 

 plate 26, fig. 742. 



Very large, subrectangular; 8-5 to 13 c.d.m. in length ; S costse and S 

 longitudinal puncta in 1 c.d.m. 



var. Gregoni CI. (A. Smithii, var. fusca Greg.), Diat. of Clyde, pi. 9, 

 f. 15*), plate 26, fig. 743. 



Elliptic, subrectangular. Length, 17 c.d.m.; 7 costal and 7 longi- 

 tudinal puncta in 1 c.d.m. 



var. delicatula Ad. Schm. (Atl., pi. 7, f. 7-8*), plate 26, fig. 744. 



Elliptic. Length, 7 to 13 c.d.m. ; 7 to 10 longitudinal costae and 10 

 to 15 longitudinal puncta in 1 c.d.m. 



var. tenuipunctata CI. (A fusca, H.V. H. in Syn. Suppl., f. 24*), 

 plate 4, fig. 153. 



6 to 9 costae and 12 to 18 longitudinal puncta in 1 c.d.m. 



var. hyperborea. (A. hyperborea Grun., Verb., 1S60, p. 531.pl. 1, f. 

 16*), plate 26, fig. 745. 



Sulci abruptly curved round the central nodule ; 7 costae in 1 c d.m. 



Marine. Bohuslan (Sweden, Grun.) Blankenberghe, H.V. H. 



forma excisa. (A. excisa Ad. Schm., Nordsee, pi. 2, f. 9*), plate 26, 

 fig. 746. 



Valve gently constricted at the median portion ; 9 costae in 1 c.d.m. 



Marine. North Sea. 



N. suborbicularis Greg, (i)iat. of Clyde, p, 15, pi. 1, f. 17*; 



in H.V.H.'s Types, No. 197), plate 26, fig. 748. 



Valve small, broadly oval-suborbicular. Costae robust. 6 in 1 c.d.m. ; 

 terminated by a large bead, not showing small beads in the intercostal spaces, 

 the Central nodule large, quadrangular, elongated. Sulci very attenuate near 

 central nodule, which they touch. Length, 4 to 5 "5 c.d.m. Breadth. 2 "5 to 



3'5 cd - m - 



Marine. Blankenberghe (H.V.H.). England, various localities. Norway. 



var. coffeaeformis Ad. Schm. (Schm. Atl., pi. 8, f. 6*), plate 26, 

 fig. 749. 



Smaller and much more delicate in all its parts. Striae, 8 to 12 

 in 1 c.d.m., feeble, delicate. Horns of nodule scarcely arcuate. 



Passes into the type by every gradation. 



Marine. North Sea. 



